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I am geologist and I have heard in 50 years petroleum will be nearly gone. I know for commercial planes there are working projects with clean energy. I can be wrong, but I think military systems would fail with no kerosene maybe in 30-40 years, as petroleum is becoming much more expensive to extract and its quality is falling.

So I wonder what's the sense of buying military appliances at 2018. I don't know if kerosene is being stored by the armies, but I wonder if it is just a madness to give the reason for increasing military budget.

I am asking also what is the future for fighter planes etc. When petroleum is finished, is there any possibility to create technology that works with nuclear energy or so or this is the end of war?

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    $\begingroup$ Even better: Use synthetic fuels. They can be made in a carbon-neutral way and are cleaner than the mineral oil based stuff. No need for nuclear options. $\endgroup$ – Peter Kämpf Jul 10 '18 at 20:03
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    $\begingroup$ When I was a kid, people kept saying that we run out of petroleum in thirty years. That was... about thirty years ago. In any case, the military will probably be one of the last users of kerosene -- unless something better is discovered, governments will be willing to pay a premium to keep their militaries fuelled with the good stuff. $\endgroup$ – David Richerby Jul 10 '18 at 20:05
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    $\begingroup$ Not from what I am hearing. The US has staggering shale oil reserves, a lot more than 50 years worth. Canada has over a trillion barrels just in the oil sands, about 1/3 recoverable today, the rest recoverable eventually, and is just starting to scratch the surface of its own shale reserves. The world has a couple centuries to run out of oil. It's just the easy to get at stuff that's running short. $\endgroup$ – John K Jul 10 '18 at 20:18
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    $\begingroup$ @Universal_learner those claims are dubious and off-topic here. $\endgroup$ – 0xdd Jul 10 '18 at 22:24
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    $\begingroup$ @Universal_learner Existing aircraft diesel engines run interchangeably on highway diesel or Jet-A/JP-1 -- no reason existing kerosene combustors couldn't run directly on bio-diesel. To run on unaltered vegetable oil would require some mods, and would carry more restrictions on operating conditions (at least for civil aviation without fuel heating). That's the beauty of a turbine -- it'll run on anything that burns. $\endgroup$ – Zeiss Ikon Jul 11 '18 at 11:00
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Petroleum isn't going to be finished for a very long time. We keep discovering and accepting trickier, dirtier, and/or costlier ways to get more oil - shale is just the last step in a long chain.

Yes, planes could be altered to use other fuels such as biodiesel. It has been done. This will require changes to the fuel system, to handle such considerably more contaminated fuel, increased fuel heating, possibly combustor alterations.

However, on a practical basis, it only makes sense to start replacing aviation fuels en masse once most road vehicles have switched to a different fuel. Aviation is weight-critical and an energy-dense fuel matters; it's also a smaller consumer than road vehicles. Also, aviation's safety and maintenance requirements call for cleaner and more consistent fuels than acceptable on the road.

For the military, fuel consumption and costs have traditionally been considered less important. It's going to get the fuel its jets need, since there will be plenty available for the foreseeable future.

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  • $\begingroup$ I guess chasis can be used at moderate poor countries as mine modifing the motor. If not, if the aircraft is going to be replaced, my country shells military systems but I won't buy anything nowadays as NATO suggests, I would use that budget to investigate the 3.0 Motors. $\endgroup$ – user32069 Jul 11 '18 at 10:43
  • $\begingroup$ Not defending it - just saying it as things are. Any threat of losing cheap private transportation sends the public supporting more invasive and dirtier methods of getting more hydrocarbons. It's not necessarily oil, just needs to be convertible into 70-170 molecular weight alkanes. Even if hydrocarbons do run out, large scale nuclear/fusion could power the production of synthetic alkanes and alcohols from water hydrolysis and carbon sources. Basically, if you have cheap enough energy, you can store it, including in liquid jet-usable form. $\endgroup$ – Therac Jul 11 '18 at 11:16
  • $\begingroup$ What I see is there is not a lot of sense to use nuclear or other energy to produce synthetic fuels and burn them, but as you say militars don't use to considere important consumtion. Anyhow, nobody talks about what happens with laboratories. Of course we will need to use energy to create organic mollecules once we have consumed what Earth gave us. If fision projects wouldn't have failed we wouldn't have any trouble, but I think the situation is not critical, but it is a huge challenge for humans, the end of petroleum natural resources. $\endgroup$ – user32069 Jul 11 '18 at 11:25
  • $\begingroup$ Note Uranium resources rounds 200 years. Then I agree with the industry at 2200 we will probably be taking energy from sun or so. $\endgroup$ – user32069 Jul 11 '18 at 11:28
  • $\begingroup$ Fusion is very long-term, but the term for "out of oil" is long too. In the meanwhile, fission scales up very well; adding breeder reactors (which are fairly competitive) can further extend the fuel supply. And there's still wind and solar. In short, we're not in immediate danger of running out of energy, just out of cheap prepackaged liquid energy. But that's a discussion going outside the scope of SE. $\endgroup$ – Therac Jul 11 '18 at 11:31
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Let's not forget that electric airplanes are starting to make headway also, along with electric cars. In 50 years, maybe a lot of small, private aviation will have switched to all electric. Not sure that's viable for large commercial aviation or the military (assuming no world peace by then).

Here's an article with some under the hood shots of the electric motor

Siemens says electric will become an industry standard by 2050 with a move to electrification already moving along much faster than the company expected.

“We might have a market ramp-up to a certified electric system by 2021, possibly before the end of 2020. We’ll be partnering with OEMs to help them integrate and maintain these electric systems,” Hamlin said.

The Chicago event also focused on how Siemens is currently working to bring electric aircraft to the marketplace, beginning with small aircraft like the Magnus and the Extra 330LE. Siemens used the Extra in 2017 to set a world speed and climb record in electric airplanes. The electrically powered Extra achieved a top speed of 211 mph and a climb record to 9,800 feet in four minutes 22 seconds.

Siemens is also blending the cyber and the physical worlds into its production process to reduce time to market for new products like a bearing shield displayed in Chicago. The shield is used in the Extra 330LE’s electric motor. When the original bearing shield was created, Siemens team created a digital twin that allowed them to continue redesigning, testing and optimizing a new version in a virtual reality world. Results were impressive as the original part was reduced in weight from 25 pounds to just 9 pounds.

The Extra 330 I believe normally flies with a 540 cubic inch flat 6 airpowered engine with 300+ horsepower. If I could fit a same-weight engine in place of my 360 cubic inch/180 HP and get 5 hour endurance, I could see switching over when my current engine was due for a major overhaul or replacement (a 25K USD to 50K USD effort). (how do we get dollar signs to appear here without messing up the following font?)

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    $\begingroup$ Don't count on the electric aircraft option anytime soon though: aviation.stackexchange.com/questions/45040/… $\endgroup$ – MadMarky Jul 11 '18 at 14:05
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    $\begingroup$ Note that the best available rechargeable battery energy density is ~300 Wh/kg (240-260 usable), while kerosene is 11,800 Wh/kg (5,000-5,500 usable). Electric may work for short-range GA with car-like fuel fractions, but a large airliner can carry as much fuel as its empty weight. Now try carrying 20 times that, and it doesn't burn off in flight. $\endgroup$ – Therac Jul 11 '18 at 14:08
  • $\begingroup$ Lot of companies are chasing it tho, with shorter range regional aircraft to start. 6 of them are highlighted in [this article][1], which also discusses swapping out battery packs for quicker turnaround time on the ground. [1]:techcrunch.com/2018/07/08/the-electric-aircraft-is-taking-off $\endgroup$ – CrossRoads Jul 11 '18 at 14:12
  • $\begingroup$ I agree comercial planes will work with clean energy. We travelers we don't need match1 speed we can always read a book or listen music $\endgroup$ – user32069 Jul 11 '18 at 14:14
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    $\begingroup$ @CrossRoads - yes, electric aircraft are perfectly fine, as long as you're not going anywhere in particular. But once you have somewhere to be, the range equation hits. Note that speed isn't in it at all. Flying from A to B is mathematically equivalent to lifting yourself by AB*L/D. $\endgroup$ – Therac Jul 11 '18 at 14:37
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In the 1950s, the US military were very interested in using high energy synthetic ethyl borane fuels, collectively known as "zip fuel", in aviation turbine engines. The XB70 Valkyrie was intended to burn "zip fuel" in it's afterburners during supersonic cruising flight. The cancellation of the USAF's HEF (High Energy Fuel) project in 1959 contributed to the cancellation of the XB70 because it effectively reduced the aircraft's operating range from 7,700 nm to 5,500, so that it could no longer attack targets in the Soviet Union without inflight refuelling. Synthetic borane fuels offer much higher specific energies than kerosene, but there are also significant disadvantages such as a tendency to spontaneous ignition in the presence of air, and the buildup of solid combustion products on turbine blades, leading eventually to engine failure. The fuels are also toxic as are the combustion products.

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There is a modified F-18 that runs on a 50% biofuel that the navy dubbed the green hornet

The military has been experimenting with biofuels and other alternative sources of energy for a while. Here is a basic demonstration model of a saltwater converter which made fuel to power a drone. The article linked mentions there are downsides that would have to be adressed like protecting surface organisms like Plankton from being sucked in.

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